Serial data communications links use signal and link conditioning to compensate for channel loss and distortion. Such serial data communications links are sometimes referred to as serdes (serializer/deserializer) links.
For example, linear equalizers (CTLE) can be used to correct for ISI (intersymbol interference). Link training/conditioning can be used to adapt equalization coefficients.
Linear equalizers are transparent to phase noise jitter (random, non-ISI, low frequency jitter). CDR (clock and data recovery) loops reject input phase noise jitter, but are inherently non-linear. Link training requires that signal conditioning devices provide linear transmission of link training (FIR) coefficients, or be protocol aware and digitally transmit the link training coefficients.